In order to ease assembling of engine functional devices to a vehicle, such as an automobile, it is known to integrally form a part of an air cleaner unit, such as an air cleaner case, an outside air introduction duct connected to the air cleaner case, and the like, with another member of the vehicle, such as an engine head cover, an intake manifold, or a fan shroud of a radiator. For example, Japanese Unexamined Patent Application Publication No. 2002-70552 describes a radiator apparatus in which an air intake duct of an air cleaner unit is integrally molded with a fan guide. Japanese Unexamined Patent Application Publication No. 2003-343371 describes an air cleaner unit in which an air cleaner case is integrated with an engine head cover.
Also, in an air cleaner unit described in Japanese Unexamined Patent Application Publication No. 2005-61382, an air cleaner case is connected to another member of a vehicle, and an air cleaner cap is coupled to the air cleaner case to cover an opening of the air cleaner case. The air cleaner case defines an outside air introduction passage through which air to be introduced to an engine flows, with the air cleaner cap. A filter element is disposed in the outside air introduction passage for filtering the air. Further, a peripheral portion of the filter element is disposed between a sealing surface of the air cleaner case and a sealing surface of the air cleaner cap, so that the filter element is held in a horizontal position, which is perpendicular to an up and down direction of the vehicle. The sealing surfaces of the air cleaner case and cap are formed on peripheries of the openings thereof and have a substantially loop shape.
In order to address a requirement of reducing a mounting space of an air cleaner unit, that is to reduce a size of he air cleaner unit, it is proposed to integrally mold an air cleaner case with another member of a vehicle, such as a fan shroud of a radiator, and to arrange a filter element in a vertical position, which is substantially perpendicular to a horizontal direction of the vehicle, in an outside air introduction passage defined in the air cleaner unit. FIG. 7 shows an example of the air cleaner unit in which the filter element is disposed in the vertical position.
The air cleaner unit shown in FIG. 7 is configured such that a filter element 101 is held by interposing a peripheral portion 102 between a sealing surface 104 of an air cleaner case 103 and a sealing surface of an air cleaner cap. Thus, it is necessary to hold the filter element 101 such that the peripheral portion 102 is in contact with the sealing surface 104 of the air cleaner case 103 while the air cleaner cap is being fixed to an opening 105 of the air cleaner case 103. Therefore, working efficiency is likely to reduce. If a worker releases his hands from the filter element 101 before the air cleaner cap is fixed to the opening 105 of the air cleaner case 103, the filter element 101 will be dropped from the air cleaner case 103, as shown by an arrow in FIG. 7.